Russell Sutton Radial Start Up Shows Promise and Required Changes

By Paul Crowe

Russell Sutton starting his radial engine

The long awaited start up of Russell Sutton's 9 cylinder radial engine has finally come about, as these videos show and it sounds just like a proper radial should. He's made some changes and additions since we last saw it, having to do with some plumbing for lubrication and the addition of a system for running the engine on LPG or propane, detailed in video one. However, as often happens with any project like this, initial operation has pointed out a few weak spots. After a short time running, an internal failure brought the engine to a halt, shown on video two.

Cylinder liner failure

The third video has the engine partially disassembled and Russell explains what failed along with his straight forward plan to get everything back together and running. Cylinder liners will be made from a more durable material and the pistons will need to be machined differently leaving a bit more of the top surface intact.

Connecting rod failure

This is the point where the successful builders keep moving forward, diagnosing problems as they arise, fixing what needs to be fixed, reassembling and trying again. You persist until you succeed. Russell has a great attitude, knowing it's far better to have these infantile failures while still on the test stand instead of under power in the airboat, the eventual location for this engine once it's been proven.

A look inside the crankcase showing the remainder of the rod and other pieces

The first time I prepped a car for painting, I had no idea what I was doing and followed the advice of someone who didn’t really know much better than I did what to do. So, all the primer came off the car just prior to painting. People kept asking me if I was upset. Non-stop they kept tip-toeing around that. Heck, I was just happy it happened BEFORE I put the paint on it. So what if I had to start over. It’s the difference between wanting something done, and wanting to learn how something is done. You never really have a failure when doing the latter. It’s simply another learning experience.

propane engines are started on vapor and switched to liquid after the converter warms up on water cooled engines, it’s not clear to me how he warmed up his converter, if it warmed up! From the looks of the damage I would say that the engine got a straight shot of propane and hydro-locked

Dennis. Inline long stroke engines have more shallow rod angles than short stroke engines . Cyl’s 8,9,1,2,3 in my engine do not need rod reliefs in the barrels with 120mm strokes. On the back side of the master rod it is a different story. Cyl’s 4,5,6.7 have much bigger rod angles which is always the case with radials. So there are higher thrust loads on these barrels. Cyl 1 with the master rod feels very large thrust loads as you realise. The liner thickness of this cyl in my engine is 4.8mm compared to barely 3mm on the rest. Big mistake not to have made them all the same. Except for two, all the link rod cly’s were about to grenade.Just happens the number nine cly went first.The heavy master rod liner saved the engine, as it held its ground when number nine blew beside it.
Different length strokes (4mm) do not cause problems. It is the geometry in this small engine that causes it. To solve the problem of late piston arrivals at TDC,(timing) radial engine master rods are ‘Compensated” As the master rod moves from TDC to BDC the piston end follows the centre line on the bore which causes the big end to rotate relative to the crankcase wall. If you look at one of the master rod photos you will notice that the number three and seven cly link rod pins are nearly 90 degrees from the master rod centre line, when the cylinders are mounted at 80degrees on the case. So the big end of the M/Rod has rotated close to 10 degrees relative to the case wall when number three and nine cly’s reach TDC. The other cly’s are similarly compensated for the M/R motion. One side of the engine mirrors the other side for link rod pin position.
So when the ignition timing is set for number one all the other cly’s will fire with the piston in the right position relative to the crank.
This is also true for the cam timing.
There are a lot of rocker arms.

Russel, thanks for your explanation. Reason for my questions was a little sketching I did you can find here: http://www.mijnbestand.nl/Bestand-UGDPHUB3UR6T.avi
Am I understanding it right when i think the timing issue is solved by adapting angles between connection points on the mainrod? If yes, how did you determine these angles?

Dennis
The link rod pin location in principal, is easy to determine. Starting at TDC cyl one, the crank is turned forty degrees at a time and the centre line of each cyl is projected onto the master rod. The distance from the centre on the crank pin to the centre of the link rod pin on the M/R is determined by the length of the link rod and gudeon pin height on the piston.
In practise it is more difficult than that. There are many things to consider when designing the hole assembly. It takes a lot of juggling to set the final pin positions.

Well at last I am now reassembling the engine with it’s beefed up liners. The extra machining work carried out to true up the decks on the crank case has been very successful ,with the cyl’s now properly aligned with the crank plane.
So barring any unforseen problems I should be able to fire the engine again in about three to four weeks.
Looking forward to running another video with some extra stuff to make it a bit more interresting.